1. Field of the Invention
The present invention relates to a method of driving a light source, a light source apparatus for performing the method and a display apparatus having the light source apparatus. More particularly, the present invention relates to a method of driving a light source capable of decreasing a current difference among light sources, a light source apparatus for performing the method and a display apparatus having the light source apparatus.
2. Description of the Related Art
Generally, liquid crystal display (LCD) devices have appealing characteristics such as thinness, light weight and power efficiency compared to other types of display devices. Thus, LCD devices are widely used to display images in various fields. An LCD device includes an LCD panel that displays an image using light transmissivity of liquid crystals and a backlight assembly disposed under the LCD panel to provide light to the LCD panel.
The LCD panel includes an array substrate having a plurality of thin-film transistors (TFTs) arranged in a matrix configuration, a color filter substrate facing the array substrate and a liquid crystal layer interposed between the array substrate and the color filter substrate.
The backlight assembly includes light sources that generate light for displaying images on the LCD panel. The light sources may be a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), a flat fluorescent lamp (FFL), a light-emitting diode (LED), etc.
The light sources are generally driven in parallel and about the same amount of current should flow through each of the light sources for a uniform distribution of luminance. However, varying degrees of voltage drop may occur due to slightly different characteristics of the light sources and the difference in the voltage drop may function as an impedance to the light sources connected in parallel. For this reason, the actual amount of current flowing through the light sources may not be equal. A current mirror circuit may be used to equalize the current levels among the light sources.
In the current mirror, a reference light source is fixed and the other light sources reproduce (or mirror) the current flowing through the reference light source. The total current is fed back based on the current flowing through the reference light source, so that the current mirror may operate only if the voltage drop of the reference light source is the highest.
For example, when the voltage drop of a light source other than the reference light source is the highest, a transistor of the current mirror circuit connected to the light source having the voltage drop higher than that of the reference light source may not be turned on, and the current may not be adjusted. Thus, the luminance between the light sources may not be uniformly distributed, adversely affecting the display quality of the display device.